KVM vs VMware vSphere

KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). It consists of a loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and a processor specific module, kvm-intel.ko or kvm-amd.ko. KVM also requires a modified QEMU although work is underway to get the required changes upstream.
VMware vSphere
Build your own cloud infrastructure in your datacenter and remote sites on VMware vSphere the world’s leading server virtualization platform. Virtualize your x86 server resources and aggregate them into logical pools for allocation of multiple workloads. Get network services optimized for the virtual environment, along with simplified administration and management. Reduce the complexity of back-end storage systems and enable the most efficient storage utilization in cloud infrastructures.